A Flexible Operated Li-ion Battery Management System for Motor Drives in Electric Vehicle Applications

Abstract:
This paper examines the problem of the cell-to-cell equalization of Li-ion batteries, and a flexible operated energy management system is proposed. Thus, the steady state and dynamic performance of a Li-ion battery can be improved by providing support to any weak and problematic cells with an adjustable equalization current according to the operating conditions of the electric vehicle motor drive. This is attained through an auxiliary energy storage system (AESS) that can act as an additional energy reservoir for enhancing the cell-to-cell equalization and providing extra energy to augment the dynamic performance of the battery in emergency conditions of the electric vehicle such as a sudden acceleration of the vehicle. Moreover, energy saving can be attained during a quick deceleration of the electric vehicle since high energy can be absorbed by the battery system through the AESS. The proposed battery management system can be properly adapted by the administrator of the electric vehicle motor drive for selectively prioritizing either the reduction of the equalization speed or the enhancement of the dynamic performance or the reduction of the energy loss during the equalization procedure by finding a correct balance in the other objectives. The battery management algorithm is realized by using the genetic algorithm (GA) method. The AESS can be materialized by either Li-ion battery cells or super-capacitors. The exact energy of the AESS depends on the support level that it required for the main Li-on battery pack. The effectiveness and applicability of the suggested Li-ion battery management system are experimentally verified.